Ethereum was proposed in late 2013 by Vitalik Buterin, a cryptocurrency researcher and programmer. Development was funded by an online crowdsale that took place between July and August 2014.
The system went live on
30 July 2015, with 11.9 million coins "premined" for the crowdsale. This accounts for about 13 percent of the total circulating supply.
So the initial release was on
JULY 30, 2015. In three months, ETH will celebrate its 3 year in cryptoworld.
source :
https://en.m.wikipedia.org/wiki/Ethereum